Lower Santa Cruz

INTRODUCTION

The Lower Santa Cruz Recharge Project (LSCRP) was developed in a partnership between Central Arizona Project and Pima County Department of Transportation and Flood Control District (Pima County). The facility was constructed in conjunction with a flood control levee along the Santa Cruz River, using State Demonstration funds. The project is located near the Marana Airport west of the Tangerine Road exit off I-10.

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LSCRP Basins Being Excavated
During Construction

Approximately 750,000 cubic yards of material was excavated from the LSCRP site and used to stabilize the bank of the Santa Cruz River to protect the Town of Marana from flooding. Following excavation of the material for the flood control district, CAP completed the recharge project by construction of the basins and the water delivery infrastructure.

The LSCRP was originally conceived as part of the Northwest Tucson AMA Replenishment Feasibility Study. The Northwest Replenishment Program began in 1994 as a cooperative effort among water resource entities in the northwest Tucson AMA to investigate recharge feasibility in the Lower Santa Cruz River and Canada del Oro Wash corridors.

The facility consists of three basins ranging from 7.4 to 11.0 acres for a total of approximately 30 acres of spreading basins. Water is delivered to the site via an open channel irrigation canal. The flow into the facility is measured utilizing a Parshall Flume.

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Parshall Flume

PROJECT FACTS

  • Permit Capacity: 50,000 AF/yr, 600,000 AF total storage
  • Cost: Total cost: $3.9 million - Cost to CAP: $1.5 million
  • Number of basins: 3 basins ranging from 7.4 to 11.0 acres for a total of 30 acres
  • Location: T12S, R11E, Section 3 NE Corner
  • Construction Completed: June 2000
  • Delivery Capacity: 65 cfs

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FACILITY COMPONENTS

LSCRP consists of three basins ranging in size from 7.4 to 11.0 acres for a total of approximately 30 acres. The water is delivered to the project using three natural gas-powered canal side pumps that are capable of pumping up to 11,000 gallons per minute each (approximately 25 cfs). The water is pumped into an open canal and conveyed approximately 1 mile from the CAP canal before being diverted into the project by manually adjusting a slide gate in the canal.

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Delivery Canal at the Diversion to LSCRP

The water that is diverted into the basins is measured at a single Parshall Flume. Flows into the individual basins are not measured. The water level in the flume is measured by a pressure transducer installed in a stilling well. Also, pressure transducers are installed in each basin to measure change in the water levels to ensure the basins don't overfill.

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Stilling Well in the Basin With a Pressure
Transducer Installed Inside (Basin 1)

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Solar Powered Remote Data Acquisition Site

All the information collected at the project is recorded at a central SCADA system via remote data acquisition units powered by solar energy. The information is relayed to the Twin Peaks Pumping Plant by radio telemetry and brought back to the CAP Control Center through the CAP microwave network.

LSCRP and AVRP are within the Federal Aviation Authority's (FAA) 10,000-foot radius of the Marana Northwest Regional Airport and, therefore, require mitigation to protect the airplanes from bird strikes. LSCRP, the larger of the two projects, employs the Phoenix Wailer that generates random noises to scare off loafing birds.

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Solar Powered Phoenix Wailer

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OPERATIONS

LSCRP began operations in June 2000 and consists of three basins totaling approximately 30 acres of recharge basins. CAP entered into a Water Transportation Agreement with BKW Farms, Inc. (BKW) to wheel water through BKW's irrigation canal system to the recharge facility. The water is measured at the CAP canal turnout with an acoustic flow meter and with a Parshall flume where the water is diverted into the recharge facility.

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BKW Farms Delivery Canal
to the Project

The infiltration rate at LSCRP has been exceptional, exceeding 7 feet per day. Only two of the basins are needed at one time to store deliveries of over 60 cfs allowing the third basin to be in a drying cycle.

The facility was originally permitted for 30,000 AF/YR but, due to the high infiltration rates, the project had to be shut down in 2001 and 2002 because the maximum annual storage volume allowed under the permit had been reached. In 2003, CAP filed a permit modification with Arizona Department of Water Resources to increase the annual amount to 50,000 AF/YR and the modification was approved in 2003.

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